Steam traps are a common item of equipment in factories, refineries and other industrial or commercial facilities. The steam traps are installed in process steam lines and act to separate condensed steam, or "condensate", from the steam without allowing the steam to escape. The separated condensate is then recycled back through condensate return lines to the boiler for conversion back to steam. To be effectively operating, the steam trap must prevent steam from escaping past the steam trap and entering the condensate return lines. If steam is allowed to pass through the steam trap into the condensate return line, the result is a loss of valuable energy and a reduction in the efficiency of the steam system.
There are several well known types of steam traps, including inverted bucket traps, float traps, thermostatic traps and disc traps. Manufacturing facilities, refineries and large buildings often are fitted with extensive systems of steam lines for heating and for process steam. Some of these facilities can contain upwards of 1,000 or more steam traps. To promote efficient operation of the steam traps, some type of monitoring or inspection is required to detect malfunctioning traps so that they can be corrected.
In the past, several different methods of checking on the condition of steam traps have been used. One system uses a battery powered probe to sense the temperature of the traps. Another system uses a battery powered probe in inverted bucket steam traps to sense the presence of water in the trap. When an inverted bucket steam trap has water in it, the trap has a state or condition referred to as "prime". A properly operating inverted bucket trap must have a condition of prime if it is functioning properly. A requisite amount of water in the trap is indicative of proper steam trap operation. A known steam trap monitoring system is disclosed in U.S. Pat. No. 4,630,633 to Vallery, which is hereby incorporated by reference. This patent discloses a probe extending into a steam trap, the probe being responsive to the level of condensate in the steam trap.
Existing steam trap monitoring schemes include systems of signal lights on the steam traps indicative of the process conditions in the traps. Such systems require visual inspection of all the steam traps in the entire manufacturing facility for proper monitoring of the steam traps. In the past, this type of manual inspection has proven to be difficult to sustain. Without a rigorously enforced inspection system, malfunctioning traps will go undetected.
Another scheme to monitor the steam traps of a facility is to provide a hard wire system, with physical wiring threaded from each of the steam traps to one or more centrally located steam trap control stations for receiving and storing data concerning the process conditions of the steam traps. It can be appreciated that in large facilities the work required to hard wire thousands of steam traps is very expensive, and in fact cost prohibitive. Hard wire systems are especially difficult to install in retrofit situations where the steam trap monitoring system is added after the facility is already built. Also, a hardwired system does not easily allow changes in the physical location of the steam traps.
It would be advantageous if a steam trap monitoring system could be devised to economically convey process condition information from a multitude of steam traps to one or more control stations. Such a system should be operable with low maintenance, and should be easy and economical to install. Further, the system not only should provide process conditions of the steam trap, but preferably should also be able to positively identify the steam trap from which the signal originates.